Corrosion prevention



July 31, 1934. A. H. J. OTT El AL CORROSION PREVENTION Filed Nov. 28,1952 FIG. 2

INVENTORS ALBARTUS HENDRIK JAN OTTO JOHAN FREDERIK VAN HOLST /TOR YPatented July 31, 1934 PATENT F Q GORRO SION PREVENTiON Albartus H drkjJan D ta and Johan F ede ik .van flolstlm asta Cu ac mDut h W st indis, assignors to n versa QilT mducts Company, Chicago, 7111., acorporation of Delaware - npplicati niNovemlie z ,1-932, Serial No,644,554

6 C a ms. v(Ci. 196-133) This invention relates to improvements corrosion prevention and more particularlyrelates to an improved method andmeans for preventing H x corrosion in refining equipment such'asfraction- 5 ators for cracked vapors. r

We have found that vapors resulting from the.

pyrolytic conversion of hydrocarbon oils contain.- ing appreciablesulphur comDOunds, acidic or other corrosive materials give troublef-romcorrosion in fractionating equipment principally in the lowerportion" of the fractionator where the temperatures-are highest and thatcorrosionjh the upper portion of the fractionator where the temperatureof the vapors has been considerably decreased, is often negligible ornon-existent.

' It has become common practice to supply the raw oil charging stock forcrackingtothe system by feeding all or a portion of it into thefractionator, where it comes into direct contact with theheated vaporousconversion products, serv+ ing to cool them and assisttheir-fractionation and being thereby pro-heated. In such processes :thereflux condensate resulting from fractionation of the vapors and 'thepreheated ;raw oil charging stock collect in the lower portion of thefractionator and are supplied therefrom to the heating elementof'thesystem for conversion. 7

The present invention, in its most specific p nbodiment, utilizes0114101136 cracked-as a means of cooling the heated vaporous conversionproducts in" the upper portion of the 'iractionator of the system tobelow a temperature at which they are corrosive and the oil thusutilized alsoser v'es as a means or" preventing corrosion of -the-wallsof thefractionator 'in its lower portion, e. that portion of the-fractionator where the vapors -reniain at a corrosive -tern-perature.{This *isaccgm pl-ished by providing a'liner -or,--more strictly, afalse shell, in the lower-portion-ofthefractionator,

spaced away from the walls of the fractionator.

The space thus provided, is kept substantially filled with oil whichenters preferably-at a low pointand overflows over the upper end of thefalse shell or liner intolthe upperportion of the ffractionator proper.The oil thus fed through the space provided between the outer walls-ofthe 'fractionator and the false shell or liner not only serves to keepthe walls or both-cooL'but also serves *asa protective body preventing'con-t'act'of not corrosive'vapors and liquid ,-with the outer shell.

"In its broader =oonceptsthe iea-tures-otthe invention are applicable-to:.use wi-th any-equipment which is subject to corrosion, particularlyi rom ina heated state andstill-moreparticularly fromfluids which areless corrosive at low temperatures. The features of the invention may,for example, be utilized to advantage in a wide variety of oil refiningequipment such as frac tionators of all'kinds, heat exchangers, scrubbers and absorbers, reactionchambers', etc, as well as f-or equipmentutilized in the paper-making and chemical industries in general. Any noncorrosive cooling medium may be utilized and preferably it is a fluidwhich will remain sub.- stantially :in :fluid form under the conditionsto which :it is subjected in the space betweenthe liner and the shell ofthe vessel which it protects. It may-or may not be desirable tointroduce the cooling .fiuid into direct contact with-thematerialsundergoing treatment in the vessel after it has passed through the spaceprovided between the wal lsof the vessel and the false shell or liner.in

the latter case it may @be simply .withdrawn'afrom the space between thewalls of the vessel and the false shell and utilized in any'desi-redmanner, or it-may benooled and-recirculated back to the inlet to saidspace. i

' novelty and featuresof the invention may bemore fully understood byreference to the -at= tached diagrammatic drawing, Figs. land 2, andthejfoilowing .descriptionflthereof. The following description ofthe-drawing includes a description of the practice of the invention asit maybe accomplished :the particular type of apparatus shown. Referring:to the drawing, Figure *1 is a cross sectional elevationof one specificdorm of #fractionator for handling hydrocarbon oils, to the principlesof the invention have been appl-ied, and"Figure-2 is a plan view of thesame .atractionator taken along a horizontal plane in- .dicated by theline 2 2 of Figure 1. The main iractionator and is spaced away f rom theinner surface of shell 1in such a manner that a ciroum ferential space 9is provided therebetween'. This space-also-exists betweenthe bottom;head of the L=falseshell and the bottom head of thef-ractionator whichare-integral with thewalls 8 and A ialse shell-ordiner 8 is -providedwithin-the 1 respectively. Suitable sleeves 10 and 11, preferably ofnon-corrosive metal, may be provided within nozzles 4 and 5respectively, as indicated in the drawing. The liner or false shell 8may be constructed of ordinary low carbon steel, or of any suitablenon-corrosive metal such. as chromesteel, or chrome-nickel steel. Theuse of noncorrosive alloys for the construction of this liner is notessential and is ordinarily unnecessary ex-. cept in extreme cases asthe cool oil c'rculated be tween the liner and the shell of thefractionator;

will ordinarily keep the liner sufficiently cool to prevent itssubstantial corrosion and, in order to assist in keeping the liner cool,as well as for economy, the liner is preferably constructed ofrelatively thin sheet metal, as compared with thickness of the outerwalls of the fractionator.

The oil utilized as the cooling medium is supplied through line 12 andvalve 13 to the space 9 between walls 1 and 8 preferably entering thisspace at a relatively low point in the fractionator, as illustrated inthe drawing. The oil-flows continuously upward through space 9 andoverflows over the upper end of false shell 8 into the central portionof the fractionator where it comes into direct contact with the vaporsarising therethrough. When desired, a perforated plate 14 or othersuitable means may be provided at the upper end of shell 8 to effectdistribution of the cooling oil across the entire cross sectional areaof the central portion of the fractionator so that substantially uniformcontact between the vapors and the cooling oil is obtained.

Preferably the quantity of the cooling oilsupplied, as described,through space 9 into the central portion of thefractionator issuificient to maintain the vapors and that portion ofthe fractionatorabove the liner or false shell 8-below a corrosive temperature or, whendesired, -addi-- tional cooling oil of the same or difierent characterthan that supplied through line 12 and valve 13 may be introducedintothe fractionator by means of line 15, valve 16 and spray coil 17, ofany suitable form, to somewhatcool the vapors prior to their contactwith the oil overflowing from space 9 to insure a sufficiently low vaportemperature immediately above shell 8. A spray coil 18 of any suitableform supplied, preferably, with a relatively light cooling oil, such asa portionof the final light distillate product of the system, throughline 19 and valve 20, may be provided in the upper portion of thefractionator to assist fractionation and to regulate the. vapor outlettemperature, 'thus controlling the end boiling point of the finaldistillate product.

The space 9 between liner 8 and shell 1 is preferably made sufficientlysmall in cross sectional area to maintain the velocity of the oilsupplied thereto through line 12 and valve 13 sufiicient to prevent itsreaching the vaporization point of any substantial quantity of this oilso that .a solid body of relatively cool oil is maintained between liner8 and shell 1.v This also servesto keep both the walls of shell 8 and 1at a minimum temperature. 7 It will be understood that the embodiment ofthe invention illustrated and described is not limited to the use of rawoil charging stock for cracking as the cooling mediumcirculated be tweenthe false shell and the outer walls of the fractionator. V For example alighter oil such asa portion of the final light distillate product ofthe system maybe utilized and circulated in sufiicient quantities andata sufficiently highvelocity to remain substantially'unvaporized untilafter its introduction into the central portion of the fractionator or,when desired, a portion of the reflux condensate or a portion of thecombined feed for the system may be cooled and circulated around theliner as a cooling medium or, in fact, any final or intermediate productof thesystem which will not contaminate the materials in thefractionator may be utilized. The exact nature of the oil is not alimiting feature of the invention although an oil is preferably usedwhich is substantially non-corrosive at the temperature attained priorto its introduction into the central portion of'the fractionator andwhich, preferably, remains substantially in the liquid-phase prior toits introduction into the central portion of the fractionator.

As a specific example of the operation of the process of the presentinvention, vapors resulting from cracking of a heavy California crudeoil containing substantial quantities of sulphur compounds are suppliedto the fractionator at a temperature of approximately 825 F. A vaporoutlet temperature of approximately 500 F. is maintained at the top ofthe fractionator. A light gauge liner of ordinary low carbon steel isutilized in the lower portion of the fractionator and the raw oilcharging stock for the system is introduced into the space between theliner and the fractionator shell at atmospheric temperature. Asufficient quantity of this cooling oil is utilized to maintain'a vaportemperature immediately above the false shell or liner at approximately650 F. As a result of this method of operation, no portion of the outershell of the fractionator shows .anysigns of corrosion upon inspectionafter approximately a years operation. A portion ofithe inner surface ofthe false shell or liner directly opposite the vapor inlet showed asmall amount of corrosion but the liner was otherwise intact. Theseresults are better appreciated by comparsion with corrosion whichresulted in the loss of about inch of metal a year in the walls of anunlined fractionator operating in conjunction with the same type ofcracking process utilizing the same type of charging stock.

It is to be understood, of course, that the sleeves 10 and 11 areremovably associated with the liner 8.

We claim as our invention:

1. In combination with an enlarged vertical chamber provided with wallssusceptible to corrosion, of a partial liner therefor spaced from thelower and bottom portions of the inner wall of the chamber to provide acircumferential space therebetween, an inlet to said liner, an outletfrom said-liner, an inlet to the chamber for charging thecircumferential space with liquid, and an outlet for discharging theliquid from said space. 2. In combination with an enlarged verticalchamber provided with walls susceptible to corrosion, of a relativelythin partial liner therefor spaced from the lower and bottom portions ofthe inner wall of the chamber to provide a circum ferential spacetherebetween, an inlet to said liner, an outlet from said liner, aninlet to the chamber for charging the circumferential space with liquid,and an outlet for discharging the liq- .uid from said space.

v 3. In, combination withan enlarged vertical chamber provided withwalls susceptible to'corrosion, of a relatively thin partial linertherefor res its

of non-corrosive material spaced from the lowerand bottom portions ofthe inner wall of the from said liner, an inlet to the chamber forcharging the circumferential space with liquid, and an outlet fordischarging the liquid from said space.

4. In combination with an enlarged vertical chamber provided with wallssusceptible to corrosion, of a relatively thin liner therefor ofnoncorrosive material spaced from the inner side and bottom walls of thechamber to provide a circumferential space therebetween and disposed inthe lower portion of said chamber, the upper end of said linerterminating a substantial distance below the upper end of the chamber,an inlet to said liner, an outlet from said liner, an inlet to thechamber for charging the circumferential space with liquid, and meansfor passing liquid from said space to the interior of said liner.

5. In combination with a vessel adapted to retain liquids and vapors fortreatment under relatively high temperatures, an inlet and outlet forsaid vessel, a non-corrosive liner mounted within the lower portion ofsaid vessel and spacedly disposed from the inner walls thereof, meansfor passing a cooling liquid into the space thus formed, and means fordispersing said cooling liquid through said vessel after its passagethrough said space.

6. In combination with a vessel adapted to retain liquids and vapors fortreatment under relatively high temperatures and superatmosphericpressures, an inlet and outlet for said vessel, a non-corrosive metallicliner mounted within the lower portion of said vessel and spacedlydisposed from the inner walls thereof, means for introducing a coolingliquidinto the space thus formed and passing the same upwardlytherethrough, and means associated with said liner for dispersing thecooling liquid through said vessel after its passage through said space.

JOHAN FREDERIK VAN HOLST. ALBARTUS HENDRIK JAN O'ITO.

